From owner-svn-src-all@FreeBSD.ORG Thu Jan 7 16:59:24 2010 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C0831106566C; Thu, 7 Jan 2010 16:59:24 +0000 (UTC) (envelope-from mavbsd@gmail.com) Received: from mail-fx0-f227.google.com (mail-fx0-f227.google.com [209.85.220.227]) by mx1.freebsd.org (Postfix) with ESMTP id C41528FC16; Thu, 7 Jan 2010 16:59:23 +0000 (UTC) Received: by fxm27 with SMTP id 27so3890663fxm.3 for ; Thu, 07 Jan 2010 08:59:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:message-id:date:from :user-agent:mime-version:to:cc:subject:references:in-reply-to :x-enigmail-version:content-type:content-transfer-encoding; bh=uO5WrjrkHwEqGKdd6QQgcOYfxqdlYkBSa4ylknVw9l4=; b=O0xEU34l7SNxrCvYMvTX6HhjKmi4bs4L/tPIKutWYUDWAE/6iqwh8CgFS1pzqk/eSk u1teJwChOUW9vgEIq23arT9yv+q4UKWQbgtB58BUJnQWqf6dL1ohHvqYyv38Cv3+wdOk hBuwtfz9hJvSneodbrJmKacpBvP1OFptvZt0s= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; b=oCUztKdJoP4QsjVT+KzSXfUlKjeEv4GrB4KyieCf4/tfuCds3s62TJXRsXPcxWRilA V/g4lmdOn3u5TS7F1o1uPA0F1qj21o5KY+3W4gYoubIV7CeZDr5rUiemFCNNDFR9nTGP tXWusc96IJCWTuizKnVfUa/T0IuUf8oJ9/BXE= Received: by 10.223.29.193 with SMTP id r1mr289509fac.29.1262883557063; Thu, 07 Jan 2010 08:59:17 -0800 (PST) Received: from mavbook.mavhome.dp.ua (pc.mavhome.dp.ua [212.86.226.226]) by mx.google.com with ESMTPS id 13sm7796508fxm.1.2010.01.07.08.59.14 (version=SSLv3 cipher=RC4-MD5); Thu, 07 Jan 2010 08:59:15 -0800 (PST) Sender: Alexander Motin Message-ID: <4B4612E2.70506@FreeBSD.org> Date: Thu, 07 Jan 2010 18:59:14 +0200 From: Alexander Motin User-Agent: Thunderbird 2.0.0.23 (X11/20091212) MIME-Version: 1.0 To: Bruce Evans References: <201001061712.o06HCICF087127@svn.freebsd.org> <9bbcef731001060938k2b0014a2m15eef911b9922b2c@mail.gmail.com> <4B44D8FA.2000608@FreeBSD.org> <9bbcef731001061103u33fd289q727179454b21ce18@mail.gmail.com> <4B450F30.20705@FreeBSD.org> <20100108013737.S56162@delplex.bde.org> In-Reply-To: <20100108013737.S56162@delplex.bde.org> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Ivan Voras Subject: Re: svn commit: r201658 - head/sbin/geom/class/stripe X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Jan 2010 16:59:24 -0000 Bruce Evans wrote: > On Thu, 7 Jan 2010, Alexander Motin wrote: >> One thing IMHO would be nice to see there is the alignment of the >> read-ahead requests to the array stripe size/offset. Dirty hack I've >> tried there, reduced number of requests to the array components by 30%. > > ffs thinks that bsize alignment is adequate. Alignment definitely should be adequate, but it is a different task. I say that bsize and stripe size are not needed to be equal, as they serve different purposes. Even with perfectly aligned usual 16K bsize and 64K stripe size we will have 75% chance of misaligned I/O. > It doesn't try to align > files any more than that. Then for sequential reads from the beginning > of the file, vfs read clustering tries to read MAXPHYS bytes at a time, > so it perfectly preserves any initial misalignment. I think we would benefit, if vfs could shrink first request of long read-ahead session a bit, to get all further MAXPHYS-sized reads to not cross more stripe boundaries then really required. In worst case it can generate one extra request to array, in best case it can twice reduce number of requests to the array components. -- Alexander Motin